Proteins · 蛋白质
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| protein/ˈprəʊtiːn/ | 蛋白质 | dàn bái zhì |
| amino acids/əˈmiːnəʊ ˈæsɪdz/ | 氨基酸 | ān jī suān |
| peptide bond/ˈpeptaɪd bɒnd/ | 肽键 | tài jiàn |
| polypeptide/ˌpɒlɪˈpeptaɪd/ | 多肽 | duō tài |
| primary structure/ˈpraɪməri ˈstrʌktʃə/ | 一级结构 | yī jí jié gòu |
The workhorses of the cell
- If DNA is the instruction manual, proteins are the machines it builds.
- Enzymes, antibodies, muscle fibres, and channels in membranes are all proteins.
- They do more different jobs than any other kind of molecule.
- And every one of those jobs comes down to a precise shape.
细胞的主力
- 如果 DNA 是说明书,蛋白质就是它构建的机器。
- 酶、抗体、肌肉纤维和膜上的通道都是蛋白质。
- 它们做的不同工作比任何别的分子都多。
- 而这每一项工作都归结为一个精确的形状。
Amino acids: 20 building blocks
- A protein 蛋白质 is a chain of small units called amino acids 氨基酸.
- There are just 20 different amino acids.
- Their order along the chain is set by a gene.
- Twenty letters, in any order and length, spell out millions of possible proteins.
氨基酸:20 种构建单元
- 蛋白质(protein)是由叫做氨基酸(amino acid)的小单元组成的链。
- 一共只有 20 种不同的氨基酸。
- 它们沿链的顺序由基因决定。
- 二十个字母,以任意顺序和长度排列,拼出数百万种可能的蛋白质。
The monomer that builds a protein is the… · 构建蛋白质的单体是……
Proteins are chains of amino acids — there are 20 different kinds. · 蛋白质是氨基酸的链——一共有 20 种不同的氨基酸。
Peptide bonds make the chain
- Amino acids join by condensation, forming a peptide bond 肽键.
- A chain of many amino acids is a polypeptide 多肽.
- Each bond releases a water molecule, just like other polymers.
- But a straight chain is not yet a working protein.
肽键组成链
- 氨基酸通过缩合连接,形成一个肽键(peptide bond)。
- 由许多氨基酸组成的链是一条多肽(polypeptide)。
- 每个键释放一个水分子,就像别的聚合物一样。
- 但一条直链还不是能工作的蛋白质。
The bond that joins two amino acids is a ____ bond. · 连接两个氨基酸的键是 ____ 键。
A peptide bond links amino acids into a chain called a polypeptide. · 肽键把氨基酸连成一条叫做多肽的链。
Folding into shape
- The chain does not stay straight — it folds into a precise 3-D shape.
- The order of amino acids is the primary structure 一级结构.
- Local coils and sheets, then the whole fold, then joined chains build the higher levels.
- That final folded shape is what lets the protein do its job.
折叠成形
- 链不会保持笔直——它折叠成一个精确的三维形状。
- 氨基酸的顺序是一级结构(primary structure)。
- 局部的螺旋和片,然后是整体折叠,再然后是连起来的链,构建更高的层次。
- 那个最终折叠的形状,让蛋白质能做它的工作。
The four levels of protein structure · 蛋白质结构的四个层次
Step up the levels — a chain of amino acids folds into a precise 3-D shape that decides the protein's job. · 一层层往上走——一条氨基酸链折叠成精确的三维形状,决定蛋白质的工作。
A protein's 3-D shape decides what job it can do. · 蛋白质的三维形状决定它能做什么工作。
Shape is everything: an enzyme's active site, an antibody's grip — all depend on the folded shape. · 形状就是一切:酶的活性位点、抗体的抓握——全都取决于折叠的形状。
Select all · 所有 true statements about proteins. · 选出关于蛋白质的所有正确说法。
Nucleic acids store the genetic code, not proteins. The other three are correct. · 储存遗传密码的是核酸,不是蛋白质。其余三条正确。
A protein's shape is fragile. High temperature or the wrong pH breaks the bonds holding the fold, and the protein denatures — it unfolds and stops working. This is why a fever is dangerous and why cooking changes egg white forever.
蛋白质的形状很脆弱。高温或错误的 pH 打断维持折叠的键,蛋白质就变性(denature)——它展开并停止工作。这就是发烧危险的原因,也是烹饪永久改变蛋清的原因。
What happens when a protein is denatured · 变性 by high heat? · 当蛋白质被高热变性时会发生什么?
Heat breaks the bonds holding the fold, so the protein denatures — it unfolds and can no longer work. · 热打断维持折叠的键,所以蛋白质变性——它展开,不再能工作。
Why shape is everything — the enzyme active site:
- An enzyme has a pocket shaped to fit one specific molecule.
- The right molecule slots in like a key in a lock.
- Denature the enzyme and the pocket loses its shape — the "key" no longer fits, and the enzyme is useless.
为什么形状就是一切——酶的活性位点:
- 酶有一个形状恰好适合某个特定分子的口袋。
- 对的分子像钥匙插进锁一样嵌进去。
- 让酶变性,口袋就失去形状——"钥匙"不再合适,酶就没用了。
Proteins are chains of amino acids joined by peptide bonds into a polypeptide. The chain folds through several levels (starting with the primary structure) into a precise 3-D shape, and that shape decides the protein's function. Heat or wrong pH denatures it, destroying the shape and the function.
蛋白质是由肽键连成多肽的氨基酸链。这条链通过几个层次(从一级结构开始)折叠成精确的三维形状,而那个形状决定蛋白质的功能。热或错误的 pH 会使它变性,破坏形状和功能。